There are various arrangements known in the art to detect end-of-fill. Each is designed to detect the end-of-fill so that the pressure to the hydraulic clutch can then be progressively increased to fully engage the hydraulic clutch thus eliminating harsh engagement of the hydraulic clutch. Harsh engagement of the hydraulic clutch results in a torque spike through the driveline of the machine, causing "jerk". This jerk is uncomfortable to the operator and also reduces the life expectancy of associated components within the powertrain of the machine.
One of the known arrangements uses a separate flow sensing valve having an electrical switch disposed thereon. The flow through the flow sensing valve is directed across a fixed orifice to the associated hydraulic clutch. Once the flow through the valve and across the fixed orifice ceases, the absence of a pressure drop across the fixed orifice permits the flow sensing valve to return to a spring biased, flow blocking position. Once the flow sensing valve reaches its spring biased position, it makes contact with an electrical switch which sends a signal to the controller indicating that the clutch is filled. This arrangement requires all flow to till the clutch be directed across a fixed orifice and also through a separate flow sensing valve. Likewise this arrangement is required for each clutch in the system.
Other known end-of-fill arrangements rely on controlling the amount of time that the flow of fluid is being directed to the clutch during filling or by controlling the fluid flow rate over a set period of time. These arrangements do not account for variances in control valves and/or clutch actuating chambers. In order to compensate for these problems, various control schemes have been devised to learn from previous clutch fills and adaptively change the fill time in order to ensure that the clutch is filled at the proper time prior to increasing the pressure to fully engage the clutch. These arrangements also require calibration of the clutches following installation which is time consuming and need special calibration schemes.
In other known end-of-fill detection systems that rely on electrical actuation of the control valve to direct fluid to fill the clutch, a controller monitors the electrical signal used to actuate the control valve. When the actuating chamber of the clutch is full, the increase in pressure acts on the control valve to move it back to a flow blacking position. The force acting to move the control valve back towards the flow blocking position is acting against the electrical force that moved the control valve to the flow passing position. This creates an electrical voltage spike which is detected by the controller. This voltage spike represents the end-of-fill. This end-of-fill detection arrangement requires a control scheme for each of the clutch control valves to detect end-of-fill in the respective clutches.
The present invention is directed to overcoming one or more of the problems as set forth above.